Micellar behavior of aqueous solutions of dodecyldimethylethylammonium bromide, dodecyltrimethylammonium chloride and tetradecyltrimethylammonium chloride in the presence of alpha-, beta-, HPbeta- and gamma-cyclodextrins

Conductivity, static fluorescence and (1)H NMR measurements have been carried out to study the micellar behavior of aqueous solutions of dodecyldimethylethylammonium bromide (DDAB), dodecyltrimethylammonium chloride (DTAC) and tetradecyltrimethylammonium chloride (TDAC) in absence and presence of alpha-cyclodextrin (alpha-CD), beta-cyclodextrin (beta-CD), hydroxypropyl-beta-cyclodextrin (HPbeta-CD) and gamma-cyclodextrin (gamma-CD). The conductivity measurements were carried out at 298.15 K. The influence of cyclodextrins on the micellar parameters, such as cmc* (apparent critical micellar concentration), beta (degree of ionization) have been analyzed. Thermodynamics of the systems was discussed in terms of the change in standard free energy of micellization, DeltaG(m)(0). Micellization was found to be less spontaneous in presence of cyclodextrins. The fluorescence intensity of the surfactant solutions is enhanced by the addition of cyclodextrins. The association constants obtained from conductivity and fluorescence data suggest the binding of gamma-CD with the surfactants to be strongest among all the cyclodextrins used. (1)H NMR chemical shift changes provide powerful means for probing the cyclodextrin-micellar interactions and inclusion of surfactant is shown by the change in the chemical shift of some of the guest and host protons in comparison with the chemical shifts of the same protons in the free compounds.     

Phase switching in Hindmarsh-Rose relay neurons

A system of Hindmarsh-Rose relay neurons with time delay coupling is considered in which the relay (central) neuron has an additional feedback term that represents the interaction activity with a local environment. The strength of environmental coupling with the central neuron plays an important role in inducing synchronization and de-synchronization between the outer neurons. The strength of feedback developed from the environmental coupling has created a gradual quenching in the oscillations of the central neuron. At a higher feedback coupling strength, oscillation of the central neuron is suppressed drastically and a transition from a regime of synchronization to out-of-phase synchronization take place between the oscillations of the two outer neurons.     

Microsphere based continuous-flow immunoassay in a microfluidic device for determination of clinically relevant insulin levels

This paper describes a miniaturized microsphere-based immunoassay integrated into a microfluidic device for rapid quantitation of insulin. Analysis of bionic pancreas studies have revealed that the rates of absorption of insulin analogs vary from patient to patient, and even within patients on different occasions. Thus development of an approach to monitor insulin continuously allows the pharmacokinetic characteristics of insulin analogs to be determined in real-time. The authors have developed a microsphere-based continuous flow assay in a microfluidic chip that allows for the detection of insulin within seconds with high sensitivity and specificity. The method was applied to near real-time monitoring of clinical samples. Calibration plot were established for different insulin analogs such as insulin aspart (Novolog), insulin lispro (Humalog), and regular human insulin (RHI) and the insulin detection limit was 0.26 ng.mL^?1 (44 pM). This sensitivity allows to detect the fasting insulin levels of T1D patients, which are reported in the range of 50–180 pM (0.3–1 ng.mL^?1), after treatment with subcutaneous insulin administration. This fast approach was also applied to sera collected in intervals from T1D patients after a bolus of insulin aspart delivery. The insulin profile obtained by this method is similar to the basal and peak insulin levels as determined using the standard non-continuous ELISA reference method. In our perception, this assay will improve healthcare by personalizing diagnostics for better clinical outcome and provide real-time feedback on sensing and actuation.

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Graphical abstract Schematic illustration of the microfluidic microsphere based Microfluidic Lab-On-Chip device for near real-time insulin monitoring.

     

Halide coordination of perhalocyclohexasilane Si6X12 (X=Cl or Br)

The addition of halide anions (X' = Cl(-), Br(-), or I(-)) to perhalocyclohexasilane Si(6)X(12) (X = Cl or Br) led to the formation of complexes comprising [Si(6)X(12)X'(2)](2-) dianions. An upfield shift in the (29)Si NMR spectra was noted upon coordination, and structural determination by X-ray crystallography showed that the dianions adopt an "inverse sandwich" structure where the six cyclic silicon atoms form a planar hexagon with the two halide anions X' located on the 6-fold axis equally disposed above and below the plane of the Si(6) ring. Additionally, these apical X' atoms are within the van der Waals bonding distance to the silicon ring atoms, indicating a strong interaction between X' and silicon atoms. These results detail crystallographic variations within the halogen series providing further insight into the nature of the Lewis acid sites above and below the Si(6)X(12) ring, where interactions with hard Lewis bases such as halide anions are observed. Interestingly, the stereochemistry of the silicon atoms in [Si(6)X(12)X'(2)](2-) is not affected much by the size or electronegativity of the halogen atoms.     

First-principles study of electronic and magnetic properties of transition metal adsorbed h-BNC2 sheets

Adsorption of Fe, Co and Ni atoms on a hybrid hexagonal sheet of graphene and boron nitride is studied using density functional methods. Most favorable adsorption sites for these adatoms are identified for different widths of the graphene and boron nitride regions. Electronic structure and magnetic properties of the TM-adsorbed sheets are then studied in detail. The TM atoms change the electronic structure of the sheet significantly, and the resulting system can be a magnetic semiconductor, semi-metal, or a non-magnetic semiconductor depending on the TM chosen. This gives tunability of properties which can be useful in novel electronics applications. Finally, barriers for diffusion of the adatoms on the sheet are calculated, and their tendency to agglomerate on the sheet is estimated.     

Glycolipids that elicit IFN-γ-biased responses from natural killer T cells

Natural killer T (NKT) cells recognize glycolipids presented by CD1d. The first antigen described, α-galactosyl ceramide (αGalCer), is a potential anticancer agent whose activity depends upon IFN-γ secretion. We report two analogs of αGalCer based on a naturally occurring glycosphingolipid, plakoside A. These compounds induce enhanced IFN-γ that correlates with detergent-resistant binding to CD1d and an increased stability of the lipid-CD1d complexes on antigen-presenting cells. Structural analysis on one of the analogs indicates that it is more deeply bound inside the CD1d groove, suggesting tighter lipid-CD1d interactions. To our knowledge, this is the first example in which structural information provides an explanation for the increased lipid-CD1d stability, likely responsible for the Th1 bias. We provide insights into the mechanism of IFN-γ-inducing compounds, and because our compounds activate human NKT cells, they could have therapeutic utility.     

Competing S(N)2 and E2 reaction pathways for hexachlorocyclohexane degradation in the gas phase, solution and enzymes

Quantum chemistry calculations have been used alongside experimental kinetic analysis to investigate the competition between S(N)2 and E2 mechanisms for the dechlorination of hexachlorocyclohexane isomers, revealing that enzyme specificity reflects the intrinsic reactivity of the various isomers.     

New Insights into Optoelectronic Features of Eu(III) Complexes with Heterocyclic Ligand for Advanced Optical Applications

Our present technological society needs the assistance of lanthanide luminescence in almost every field to meet the global energy demands. In present research work we have synthesized five (one binary and four ternary) 5-(4-methylphenyl)-2- furoic acid based Eu(III) complexes with ancillary ligands, namely, aqua (H₂O), neocuproine (neo), 2, 2’-bipyridyl (bipy), bathophenanthroline (batho) and 1, 10-phenanthroline (phen). The spectroscopic analysis and photophysical features are characterized by the use of different investigative techniques. All the findings obtained from EDAX, elemental (CHN) analysis, FT-IR, NMR, UV–visible spectroscopy declared the coordination of ligand binding sites with the europium ion. These Eu(III) complexes possess good thermal stability and excellent optoelectronic features as predicted with the help of TGA and PL analysis. Diffuse reflectance spectral studies confirm their applications in the wide band gap semiconductors. The Judd–Ofelt analysis and monoexponential behavior of lifetime reveals the existence of asymmetric and single local environment around europium ion. All the complexes show sharp red emission validated by CIE color coordinates, color purity, asymmetric ratio and CCT values. SEM analysis tells that the bulk of these complexes comprised of spherical shaped particles with uniform distribution.

     

Amplitude death in nonlinear oscillators with indirect coupling

We investigate the effect of frequency mismatch in two indirectly coupled Rössler oscillators and Hindmarsh–Rose neuron model systems. While identical systems show in-phase or out-of-phase synchronization states when coupled through a dynamic environment, mismatch in the internal frequencies of the systems drives them to a fixed point state, i.e., amplitude death. There is a region in the parameter space of the frequency mismatch and coupling strength where system shows amplitude death. The numerical results of Rössler system are also experimentally verified using piece-wise Rössler circuits.